1. Field of the Invention
The present invention refers to an apparatus for producing spirally wound, i.e. coiled wire springs of a universally known kind, which are made by appropriately processing and cutting an elongated section of continuous wire, frequently wound into a skein form.
2. Description of the Related Art
In the following description, these springs will be referred to simply as wire springs, i.e. the term “wire spring” is used to indicate and include all springs of the above-cited kind.
Wire springs are largely known to be generally produced by winding about an appropriate rod, which is called a “core” in the technical parlance, a length of continuous wire that is then appropriately cut into individual sections, i.e. discrete springs. The cut end of a just produced spring forms at the same time the cut end of the next spring being formed.
It is well known to all those skilled in the art—and it will in fact be only briefly mentioned here—that an automatic machine for the production of such wire springs comprises in particular (and with special reference to FIG. 7):                a first working station 1 provided with a substantially cylindrical support member 2 adapted to enable a length of wire 4 to be wound around a certain portion thereof, and cutting means 3 provided at said first working station and adapted to cut said length of wire against said support used as an anvil,        a second working station 5 provided with a rod 6 for supporting and winding said wire, and means 7 for engaging and clamping a portion of said wire at an end portion of said rod 6,        a wire carriage 9 adapted to transfer a length of wire from said first working station to said second working station with a movement that is substantially rectilinear and parallel to the direction of the axis X of said rod.        
The production of wire springs with such kind of apparatus allows a high degree of manufacturing flexibility, as well as considerable productivity rates. However, this particular machine, along with the wire-working process performed on it, is not free from certain peculiar drawbacks that will be described in greater detail below:
a) A first drawback derives from the fact that the means used to clamp the wire onto the rod (core), and known also as the “claw” in the art, is constituted by a single member that, in order to clamp the wire, must penetrate it and, as a result, must be sharp-pointed; owing to its being used continuously under heavy-duty conditions, this member is subject to rapid wear and tear, so that it must be replaced quite frequently; as an alternative solution, provisions can be taken in order to be able to periodically adjust the pressure of said claw, but even this measure, which does not solve the problem in any permanent, lasting manner, has a drawback in that it requires additional operations to be carried out and the manufacturing process, which is usually fully automated, must be interrupted accordingly,
b) A second drawback more specifically relates to the actual way in which said claw works: since it must press against the wire, which is wound around the core, the latter undergoes a lateral bending stress that causes the spring to be wound according to an axis that, as a result, becomes neither stable nor rectilinear, thereby introducing obvious problems as far as the regularity of the springs being produced is concerned.
This drawback becomes increasingly significant as the diameter of the core decreases and the diameter of the wire being worked increases, since, as anyone skilled in the art is well aware of, when the above conditions are amplified accordingly, the need arises for the pressure of the claw onto the wire to be markedly increased, thereby aggravating the working conditions of the core to quite a considerable extent.
c) A third drawback is brought about by the fact that the pressure exerted by the clamping claw unavoidably causes an impression to be left at an end portion of the spring, which tends to introduce some weakening effect in the same spring and may sometimes cause some problems,
d) A fourth drawback derives from the fact that this lateral pressure exerted on the first coil of the spring causes—and this is again largely known to all those skilled in the art—said first coil to be shaped so as to show a slight, but measurable ovalness, instead of the desired perfect circularity; even such irregularity tends to quite frequently cause problems in assembling and using the springs.
The state of art regarding the manufacturing processes used to produce spirally wound springs, i.e. coiled wire springs, lists a great variety of technologies and related plants; by mere way of example, the cases may be cited here of the disclosures in the Japanese patent applications nos. JP 06079869 and JP 05082609, as well as the Italian patent no. IT 1.181.049. The latter, in particular, discloses a fully automated process for making coiled wire springs without initial and final stems; however, none of the elements and features disclosed in this patent or, more generally, in the state of the art, enables any of the afore-noted drawbacks and problems to be solved, actually.